1. Field of the Invention
The present invention relates to a measuring apparatus and a measuring method of detecting color condition of a coloring member (e.g., a thermo-sensible liquid crystal) whose color condition changes according to change of physical quantity (e.g., temperature), and for calculating the physical quantity thereof on the basis of tristimulus values of the color of the coloring member.
2. Description of the Prior Art
A prior art temperature measuring apparatus related to the present invention will be described hereinbelow by taking an example of thermo-sensible liquid crystal which is widely used as a coloring member whose color condition changes according to change of the physical quantity thereof.
When various products are searched or designed, there are many cases where it is required to know a wide temperature distribution on or over the surface of an object. In these cases, in general, it is necessary to arrange a number of thermometers (e.g., thermo couples) for measuring the temperature distribution on or over the surface of the object to be measured. In this method, however, when the thermometers are arranged in contact with the object to be measured, the object to be measured is subjected to unnecessary disturbance. Therefore, when there exists an air flow in the vicinity of the surface of the object, there arises a problem in that the temperature field of the measured object is distorted due to the disturbance caused by the thermometers themselves. In addition, there exists such a difficulty that the measurement points must be previously specified on the surface of the measured object. Further, as a matter of course, there exists a limit of the number of the measurement points, because data obtained at the measurement points must be all processed.
On the other hand, there exists a non-contact surface measurement method, for instance such as radiation thermometer or infrared thermo-camera. In this method, the temperature distribution can be measured in a relatively wide range. In this non-contact method, however, the cost of the instrument is as high as several millions yen or higher.
Due to the above-mentioned background, as a relatively low-costly method of measuring a temperature field extending in two- or three-dimensions on the surface of an object to be measured, a method of using a liquid crystal (thermo-sensible liquid crystal) having such a feature that the color changes according to temperature thereof has been widely developed. In this method, the measured color data are detected by a CCD camera and then inputted to a computer for image processing.
In the method of using a thermo-sensible liquid crystal, wide temperature data can be obtained on the basis of the correspondence between the color and the temperature obtained by quantitatively processing the color change of the liquid crystal. In this method, however, since the relationship between the color data (e.g., RGB values) and the temperature is represented by an extremely complicated non-linear function in general as shown in FIG. 7, various methods of deciding the color and the temperature unequivocally and quantitatively have been so far proposed.
For instance, Kasagi, et al., have succeeded in obtaining an isothermal line on a measured surface by irradiating the liquid crystal surface with a monochromatic light source and by clearly visualizing only the temperature range corresponding to a wavelength (Kasagi, Hirata, Kumata; JSME International Journal Series B, Vol. 48 No. 430 (1982)).
Further, Kunugi, et al. have developed the Kasagi's method by use of white light having a uniform spectrum as the light source and by use of a plurality of optical filters each having an extremely narrow transmission wavelength range, to decide each isothermal line which corresponds to each transmission wavelength in sequence, so that a plurality of isothermal lines can be obtained in sequence by a single experiment (Kunugi, Ueda, Akino; JSME International Journal Series B, Vol. 53 No. 485 (1987)).
Further, recently, Kimura et al. have reported a method of obtaining the correspondence between temperature and color by allowing a neural network to learn the RGB values of the color image data changing according to temperature (Kimura, Uchide, Ozawa; Proceeding of Japan Visualization Association Vol. 12, Suppl. No. 1, pp. 7-10 (1992)).
Further, Farina, et al. have proposed such a method of obtaining the correspondence between color and temperature by obtaining HSI values (Hue, Saturation, and Intensity) of the color image data changing according to temperature and by noting the Hue values having a wide one-valued function range with respect to temperature (Farina, Hacker, Moffat. Eaton; Exp. Thermal Fluid, Sci. 9,1-12. (1994)).
In the Kasagi et al. method, however, it is necessary to set the heat transfer surface to various temperature levels in order to obtain a plurality of isothermal lines. Further, in the Kunugi et al. method which improves the Kasagi et al. method, although a plurality of isothermal ranges can be decided by only a single experiment, since a number of filters are necessary, there exists a problem in that the measurement work is rather complicated.
Further, in the Kimura et al. method, although the subsidiary devices such as filters can be eliminated, since a plurality of learning patterns must be determined and further a great number of learning operations must be repeated, there arises another problem in that a relatively long time is needed in the pre-processing.
Further, in the Farina et al. method, although the corresponding range between color and temperature can be tended on the basis of the newly-defined Hue values, the range where temperatures and Hue values can be represented on the basis of a one-valued function cannot be extended all over the coloring area, so that this method is not a method of measuring the temperature of the liquid crystal all over the coloring area of the liquid crystal, with the result that the measured temperature range is inevitably narrowed.
As described above, in the temperature measuring methods using the thermo-sensible liquid crystal so far proposed, there have been various problems in that complicated processing is necessary to obtain the correspondence between color data and temperature and in addition the colored area of the thermo-sensible liquid crystal is not sufficiently utilized.
In addition, in the prior art magnetic disk apparatus, there exists the following problem when a gap width between an magnetic head and a magnetic disk is measured:
Prior to the description of this problem, a flying head slider used for the magnetic disk apparatus will be explained hereinbelow, as an example of the prior art measuring apparatus used for the magnetic disk apparatus.
In the case of a magnetic disk apparatus used as an external memory apparatus of a computer, it is necessary to fly the magnetic head from the magnetic disk by a micro height in data recording and reading operation. With the advance of the high density of the magnetic disk apparatus, recently, this flying height has become as small as 0.1um or less.
Here, since the change of the flying height of the magnetic head is directly related to a recording characteristic of the apparatus, it is important to check whether the magnetic head can be kept-flown by a micro distance away from the magnetic disk during the development or researching of the recording apparatus as described above.
As the method of measuring the micro gap such as the flying height of the magnetic head from the magnetic disk, a method has been so far proposed, by which light of a known wavelength is irradiated upon a measured surface to obtain an interference fringe (or pattern) formed on the measured surface. In this method, however, there exists a problem in that the gap can be measured only when the gap corresponds to integer times of 1/4 wavelength of the incident light.
To overcome this problem, Tanaka and Sugawara have proposed the following method, as disclosed in Japanese Published Unexamined (Kokai) Patent Application No. 61-44307. In this method, a gap between the magnetic head and the magnetic disk can be measured on the basis of an interference fringe as follows: the interference fringe can be obtained by irradiating white light onto the measured surface (e.g., the magnetic disk) through an optical head; the interference colors produced by the measured surface are photographed with the use of a TV camera; the hue components composed of R, G and B signals generated by the TV camera are obtained; and the obtained hue component values are compared with the reference values on the basis of the previously determined relationship between the gap and the hue component values by executing various calculations (as shown in FIG. 13).
Further, Kubo has proposed the following method, as disclosed in Japanese Published Unexamined (Kokai) Patent Application No. 63-290903. In this method, in the same way as above, the flying height of the magnetic head from the magnetic disk can be obtained, by irradiating light upon the measured surface, by photographing interference colors by a TV camera, by obtaining hue components on the basis of R, G and B signals obtained by the TV camera, and by comparing the obtained hue components with the reference hue components on the basis of the previously obtained relationship between the hue components and the gap.
Both the above-mentioned methods are different from each other only in the used transform formulae for obtaining hue values on the basis of R, G and B signals. In both the methods, the micro gap can be measured continuously. In these methods, however, when the hue values are obtained on the basis of the R, G and B signals, since the complicated discriminants are required according to the mutual relation between R, G and B signals, there still exists a problem in that complicated signal processing must be executed.